Resisting paste, resistor, and electronic parts

ABSTRACT

A resistor paste comprising glass material substantially free of lead, conductive material substantially free of lead, organic vehicle, and NiO and/or perovskite type crystal structured oxide. Oxides having perovskite type crystal structure can be CaTiO 3 , SrTiO 3 , BaTiO 3 , NiTiO 3 , MnTiO 3 , CoTiO 3 , FeTiO 3 , CuTiO 3 , MgTiO 3  or so. A content of glass material is 60 vol % or more and less than 91 vol %, or 63 to 88 vol % or less, and a content of conductive material is 8 vol % or more and 32 vol % or less, and a content of said NiO is more than 0 vol % and 12 vol % or less.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a resistor paste, a resistor, and anelectronic device.

2. Description of the Related Art

A resistor paste is generally mainly comprised of a glass material, aconductive material, and an organic vehicle (binder and solvent). Theglass composition is included for adjusting the resistance value andhaving adhesion. The resistor paste is printed on a substrate, thenfired to form a thick-film (10 to 15 μm or so) resistor.

Most of conventional resistor paste usually contains lead oxide-basedglass as the glass material and ruthenium oxide or a compound ofruthenium oxide and lead as a conductive material and therefore is aleaded paste.

However, the leaded resistor paste is not desirable for an environmentalpollution. Therefore, various proposals have been made for a lead freethick-film resistor paste, e.g. Japanese Patent Publication (A) No.H08-253342.

Normally, a thick-film resistor paste with a high resistance, i.e. 100kΩ/□ or more generally shows temperature coefficient of resistance (TCR)of negative value. Accordingly, an additive such as CuO is added as TCRadjustment in order to make TCR close to zero. Various proposals aremade for TCR adjustment, e.g. Japanese Patent Publication (A) No.S61-67901.

However, said method is introduced for glasses comprising lead,therefore, when the method, which is to add additives such as CuO, isintroduced for resistor pastes comprising lead free conductive materialand lead free glass material, it was difficult to adjust itscharacteristic with said conventional method. Deterioration in shorttime overload (STOL) characteristics occurred when TCR was adjusted.

DISCLOSURE OF THE INVENTION

An object of the invention is to provide a lead free resistor pastesuitable for obtaining a resistance with a small value of bothtemperature coefficient of resistance (TCR) and short time overload(STOL) characteristics. Further object of the present invention is toprovide a resistor paste enabling a high resistance value and smallvalues of both temperature coefficient of resistance (TCR) and shorttime overload (STOL) characteristics, and an electric device having theresistor paste, such as circuit board.

In order to achieve the above-mentioned object, a resistor pasteaccording to the first object of the present invention comprises glassmaterial substantially free of lead, conductive material substantiallyfree of lead, organic vehicle and NiO as an additive.

Note that in the present invention, “substantially free of lead” meanslead as impurity of 0.05 vol % or less may be included in the glassmaterial or conductive material.

A resistor according to the first object of the present inventioncomprises glass material substantially free of lead, conductive materialsubstantially free of lead, and NiO as an additive.

An electric device according to the first object of the presentinvention comprises electric device having resistor and said resistorcomprises glass material substantially free of lead, conductive materialsubstantially free of lead, and NiO as an additive.

In the first object of the present invention, preferably, a content ofsaid glass material is 60 vol(volume)% or more and less than 91 vol %,and a content of said conductive material is 8 vol % or more and 32 vol% or less.

In the first object of the invention, preferably, a content of said NiOis more than 0 vol % and 12 vol % or less, more preferably, 2 vol % ormore and 12 vol % or less.

In the first object of the invention, preferably, CuO is further addedfor an additive and a content of said CuO is more than 0 vol % and 8 vol% or less. Here, preferably, a content of said NiO is 2 vol % or moreand 12 vol % or less, and a content of said CuO is 1 vol % or more and 2vol % or less.

A resistor paste according to the second object of the inventioncomprises a glass material substantially free of lead, a conductivematerial substantially free of lead, organic vehicle, and a perovskitetype crystal structured oxide as an additive.

A resistor according to the second object of the invention comprises aglass material substantially free of lead, a conductive materialsubstantially free of lead, and a perovskite type crystal structuredoxide as an additive.

An electric device according to the second object of the presentinvention comprises electric device having a resistor and said resistorcomprises glass material substantially free of lead, conductive materialsubstantially free of lead, and a perovskite type crystal structuredoxide as an additive.

According to the second object of the invention, an oxide having aperovskite type crystal structure (a crystal structure expressed by“ABX₃”) may be a defect perovskite or a composite perovskite other thana simple perovskite such as CaTiO₃, SrTiO₃, BaTiO₃, CaZrO₃, SrZrO₃,NiTiO₃, MnTiO₃, CoTiO₃, FeTiO₃, CuTiO₃, MgTiO₃ or so. Of all thoseoxides, at least one from SrTiO₃, BaTiO₃ or CoTiO₃ can be used.

According to the second object of the invention, preferably, a contentof said glass material is 63 vol % or more and 88 vol % or less(preferably 84 vol % or less) and a content of said conductive materialis 8 vol % or more and 30 vol % or less.

According to the second object of the invention, CuO may be included anda content of said CuO is preferably more than 0 vol % and 8 vol % orless.

According to the second object of the invention, preferably, a contentof said oxide having a perovskite type crystal structure is more than 0vol % and 13 vol % or less. More preferably, a content of said oxidehaving a perovskite type crystal structure is 1 vol % or more and lessthan 12 vol %. In this case, preferably, a content of said CuO is 1 vol% or more and less than 8 vol %.

Note that when said oxide having a perovskite type crystal structure isCaTiO₃, preferably a content of said CaTiO₃ is 2 vol % or more and lessthan 12 vol %, and a content of said CuO is 2 vol % or more and lessthan 8 vol %.

According to the second object of the invention, NiO may be furtherincluded as an additive and a content of said Ni is preferably more than0 vol % and 12 vol % or less, more preferably, 2 vol % or more and 12vol % or less.

The present invention described below, including the first and thesecond objects of the invention, preferably further include MgO as anadditive and a content of said MgO is 2 vol % or more and 8 vol % orless.

Preferably, a content of said NiO is more than 0 vol % and 12 vol % orless and more preferably, 2 vol % or more and 12 vol % or less.

Preferably, ZnO is further included as an additive and a content of saidZnO is 1 vol % or more and 4 vol % or less.

Preferably, said glass material comprises

A group comprising at least one kind from CaO, SrO, BaO, and MgO,

B group comprising B₂O₃ and/or SiO₂,

C group comprising ZrO₂ and/or Al₂O₃.

Preferably, said glass material comprises D group comprising at leastone kind from ZnO, MnO, CuO, CoO, Li₂O, Na₂O, K₂O, P₂O₅, TiO₂, Bi₂O₃,V₂O₅ and Fe₂O₃.

Preferably, contents of said groups are;

A group: 20 mol % or more and 40 mol % or less

B group: 55 mol % or more and 75 mol % or less

C group: more than 0 mol % and less than 10 mol %

Preferably, a content of said D group is 0 mol % or more and 5 mol % orless.

Preferably, said conductive material comprises RuO₂ or complex oxides ofRu.

Preferably, the ratio (W2/W1) between the weight (W1) of all the powdersof glass material, conductive material, and additives, and the weight(W2) of the organic vehicle is preferably 0.25 to 4.

In the present invention, a resistor paste is prepared by addingparticular additives such as NiO, or perovskite type crystal structuredoxide such as CaTiO₃ to a lead free conductive material and a lead freeglass material. Therefore, said prepared resistor is possible to realizea high resistance value of for example 100 kΩ/□ or more, preferably1MΩ/□ or more, and suppress an absolute value of TCR of for example lessthan ±150 ppm/° C., preferably ±100 ppm/° C., and further STOLcharacteristics of for example less than ±7%, preferably less than ±5%.Namely, a resistor prepared by the resistor paste as in the presentinvention can maintain its superior characteristics even whensurrounding temperature or impressed voltage varies which leads theresistor highly useful.

A resistor according to the present invention can be applied to anelectrode part of a capacitor or a inductor other than a single layer ormultiple layer circuit board.

An electric device according to the present invention is notparticularly limited, but for example, a circuit board, capacitor,inductor, chip resistor, or an isolator may be mentioned.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Below, the present invention will be explained in detail based onexamples of the invention.

The First Embodiment

A resistor paste according to the first embodiment of the presentinvention comprises glass material substantially free of lead,conductive material substantially free of lead, organic vehicle, and NiOas an additive.

Said glass material substantially free of lead is not particularlylimited but preferably comprising at least one kind from CaO, SrO, BaO,and MgO, B group comprising B₂O₃ and/or SiO₂, C group comprising ZrO₂and/or Al₂O₃. With these glass materials of groups A to C, even withoutlead, the STOL characteristics tend to improve. More preferably, saidglass material further comprises D group comprising at least one kindfrom ZnO, MnO, CuO, CoO, Li₂O, Na₂O, K₂O, P₂O₅, TiO₂, Bi₂O₃, V₂O₅, andFe₂O₃. By including D group in said glass material, the TCR and the STOLcharacteristics tend to improve.

In this case, contents of said each group is;

A group: 20 mol % or more and 40 mol % or less

B group: 55 mol % or more and 75 mol % or less

C group: more than 0 mol % and less than 10 mol %

D group: 0 mol % or more and 5 mol % or less, and more preferably;

A group: 25 mol % or more and 35 mol % or less

B group: 58 mol % or more and 70 mol % or less

C group: 3 mol % or more and 6 mol % or less

D group: 2 mol % or more and 5 mol % or less.

With these contents, the STOL characteristics tend to improve.

Contents of these glass materials are preferably, 60 vol % or more andless than 91 vol % and more preferably, 70 vol % or more and 89 vol % orless. If the contents of these glass materials are too small, theresistance tends to become too low, and if too large, the resistancetends to become too high.

Conductive material substantially free of lead is not particularlylimited but other than ruthenium oxide, an Ag—Pd alloy, TaN, LaB₆, WC,MoSiO₂, TaSiO₂, and metals such as Ag, Au, Pd, Pt, Cu, Ni, W, and Mo maybe mentioned. These substances may be used alone or in combinations oftwo or more types. Among these, an oxide of ruthenium is preferable. Asthe oxide of ruthenium, ruthenium oxide (RuO₂, RuO₃, RuO₄) and also aruthenium-based-pyrochlore (Bi₂Ru₂O_(7-x), Tl₂Ru₂O₇, etc.) or acomposite oxide of ruthenium (SrRuO₃, CaRuO₃, BaRuO₃, etc.) etc. areincluded. Among these, oxide of ruthenium or a composite oxide ofruthenium is preferable and RuO₂, SrRuO₃, CaRuO₃, and BaRuO₃ are morepreferable. With these conductive materials, even without lead, the STOLcharacteristics tend to improve.

Contents of these conductive materials are preferably 8 vol % or moreand 32 vol % or less, more preferably 8 vol % or more and 28 vol % orless. If the contents of these conductive materials are too small, theresistance tends to become too high and the STOL characteristics tend todeteriorate, and if too large, the resistance tends to become too low.

Organic vehicle is prepared by dissolving binder in an organic solvent.Said binder is not particularly limited but suitably selected from allkinds of general binders such as ethyl cellulose and polyvinyl butyral.Organic solvent used is not particularly limited but suitably selectedfrom all kinds of organic solvent such as terpineol, butyl carbitol,acetone, toluene, and other organic solvents may be suitably selected.

The first embodiment of the present invention is characterized in thatincluding NiO as an additive. Therefore, the TCR and the STOLcharacteristics of obtained resistor can be well balanced. The contentof NiO is more than 0 vol % and 12 vol % or less, more preferably, 2 vol% or more and 12 vol % or less.

The first embodiment of the present invention is preferable to furtherinclude CuO as an additive. CuO is an adjustment of the TCR. In thiscase, a content of CuO is more than 0 vol % and 8 vol % or less, morepreferably 1 vol % or more and 2 vol % or less. If an amount of CuOadded increases, STOL characteristics tend to deteriorate.

The first embodiment of the present invention is preferable to furtherinclude MgO as an additive. MgO is an adjustment of the TCR. In thiscase, a content of MgO is 2 vol % or more and 8 vol % or less, morepreferably 4 vol % or more and 8 vol % or less. If an amount of MgOadded increases, the STOL characteristics tend to deteriorate.

The other additives used for TCR adjustments are, for instance, MnO₂,V₂O₅, TiO₂, Y₂O₃, Nb₂O₅, Cr₂O₃, Fe₂O₃, CoO, Al₂O₃, ZrO₂, SnO₂, HfO₂,WO₃, Bi₂O₃ or so.

A resistor paste may be prepared by adding organic vehicle to conductivematerial, glass material, and all kinds of additives, then, mixed by athree roll mill or so. Note that the ratio (W2/W1) of the total weight(W1) of all the composition powders of the glass material, theconductive material, and additives, and the weight (W2) of an organicvehicle is preferably a weight range of 0.25 to 4, and more preferably0.5 to 2. When the ratio (W2/W1) is too low, it becomes difficult tomake paste and paste viscosity tends to increase, and when too high, thepaste viscosity tends to become lower than a viscosity suitable for ascreen-printing.

Resistor paste as mentioned above may for example be screen-printed on asubstrate, such as alumina, glass ceramics, dielectric, AIN, etc.,dried, then, fired at a temperature of around 800 to 900° C. for 5 to 15minutes to obtain resistor.

The obtained resistor comprises glass material substantially free oflead, conductive material substantially free of lead, and NiO as anadditive. Thickness of the resistor film may be thin but normally 1 μmor more, preferably around 10 to 15 μm or so.

The resistor according to the present embodiment can be applied to anelectrode part of a capacitor or a inductor other than a single layer ormultiple layer circuit board.

The Second Embodiment

A resistor paste according to the second embodiment of the presentinvention comprises glass material substantially free of lead,conductive material substantially free of lead, organic vehicle, andCaTiO₃ as an additive.

Said glass material substantially free of lead, conductive materialsubstantially free of lead, and organic vehicle are the same as those inthe first embodiment of the invention. The content of the organicvehicle as in the second embodiment of the invention is the same withthat of the first embodiment of the invention. However, the contents ofboth glass material and conductive material as in the second embodimentdiffer from those of the second embodiment.

Content of this glass material according to the second embodiment of theinvention is preferably, 63 vol % or more and 84 vol % or less and morepreferably, 70 vol % or more and 84 vol % or less. Further, content ofconductive material is preferably 8 vol % or more and 30 vol % or lessand more preferably, 8 vol % or more and 26 vol % or less.

The second embodiment of the present invention is characterized in thatincluding CaTiO₃ as an additive. With this CaTiO₃, as is the same withNiO of the first embodiment of the invention, the TCR and the STOLcharacteristics of obtained resistor can be well balanced. The contentof CaTiO₃ is preferably more than 0 vol % and 13 vol % or less, and morepreferably, 2 vol % or more and less than 12 vol %.

The second embodiment of the present invention is also preferable tofurther include CuO as an additive. CuO is an adjustment of the TCR asis the same with the first embodiment of the invention. In this case,preferably, a content of CuO is more than 0 vol % and 8 vol % or less,and more preferably, 2 vol % or more and less than 8 vol %.

The second embodiment of the present invention is preferable to furtherinclude ZnO as an additive. ZnO is an adjustment of the TCR. In thiscase, preferably, a content of ZnO is 1 vol % or more and 4 vol % orless, more preferably 2 vol % or more and 4 vol % or less. When anadditive of ZnO increases, the STOL characteristics tend to deteriorate.

Further, as is the same with the first embodiment of the invention,additives other than the above-mentioned additives may further be added.Other compositions, manufacturing methods, and effects of this secondembodiment of the invention are the same with those of the firstembodiment of the invention.

The Third Embodiment

A resistor paste according to the present invention comprises glassmaterial substantially free of lead, conductive material substantiallyfree of lead, organic vehicle, and perovskite type crystal structuredoxide other than CaTiO₃ as an additive.

Said glass material substantially free of lead is the same with that ofthe first embodiment and is not particularly limited, but preferablycomprising A group selected at least one kind from CaO, SrO, BaO, andMgO, B group comprising B₂O₃ and/or SiO₂, and C group comprising ZrO₂and/or Al₂O₃. More preferably, said glass material further comprises Dgroup comprising at least one kind from ZnO, MnO, CuO, CoO, Li₂O, Na₂O,K₂O, P₂O₅, TiO₂, Bi₂O₃, V₂O₅, and Fe₂O₃.

In this case, contents of said each group is;

A group: 20 mol % or more and 40 mol % or less

B group: 55 mol % or more and 75 mol % or less

C group: more than 0 mol % and less than 10 mol %

D group: 0 mol % or more and 5 mol % or less, and more preferably;

A group: 25 mol % or more and 35 mol % or less

B group: 58 mol % or more and 70 mol % or less

C group: 3 mol % or more and 6 mol % or less

D group: 2 mol % or more and 5 mol % or less.

Conductive material substantially free of lead is the same with those inthe first embodiment of the invention and not particularly limited, butother than ruthenium oxide, an Ag—Pd alloy, TaN, LaB₆, WC, MoSiO₂,TaSiO₂, and metals such as Ag, Au, Pd, Pt, Cu, Ni, W, and Mo may bementioned. These substances may be used alone or in combinations of twoor more types. Among these, an oxide of ruthenium is preferable. As theoxide of ruthenium, ruthenium oxide (RuO₂, RuO₃, RuO₄) and also aruthenium-based pyrochlore (Bi₂Ru₂O_(7-x), Tl₂Ru₂O₇, etc.) or acomposite oxide of ruthenium (SrRuO₃, CaRuO₃, BaRuO₃, etc.) etc. areincluded. Among these, oxide of ruthenium or a composite oxide ofruthenium is preferable and RuO₂, SrRuO₃, CaRuO₃, and BaRuO₃ are morepreferable.

Contents of these glass materials are preferably, 63 vol % or more and88 vol % or less and more preferably, 70 vol % or more and 84 vol % orless. And contents of these conductive materials are preferably, 8 vol %or more and 30 vol % or less and more preferably, 8 vol % or more and 26vol % or less.

The present embodiment is characterized in that comprising perovskitetype crystal structured oxide other than CaTiO₃ as an additive. Withthis oxide, the TCR and the STOL characteristics of obtained resistorcan be well balanced. Such perovskite type crystal structured oxides arepreferably selected from NiTiO₃, MnTiO₃, CoTiO₃, FeTiO₃, CuTiO₃, MgTiO₃,SrTiO₃, and BaTiO₃. Content of perovskite type crystal structured oxidesother than CaTiO₃ is preferably more than 0 vol % and 13 vol % or less,more preferably, 1 vol % or more and less than 12 vol %, and the mostpreferably, 2 vol % or more and less than 12 vol %.

The present embodiment is preferable to further include CuO and/or NiOas an additive. CuO is a TCR adjustment. In this case, content of CuO ispreferably more than 0 vol % and 8 vol % or less, and more preferably, 1vol % or more and less than 8 vol %, the most preferably, 2 vol % ormore and less than 8 vol %. If an addition amount of CuO increases, theSTOL characteristics tend to deteriorate.

The present embodiment is preferable to further include ZnO as anadditive. ZnO is a TCR adjustment. In this case, content of ZnO ispreferably 1 vol % or more and 4 vol % or less, more preferably, 2 vol %or more and 4 vol % or less. If an addition amount of ZnO increases, theSTOL characteristics tend to deteriorate.

The present embodiment is preferable to further include MgO as anadditive. MgO is a TCR adjustment. In this case, content of MgO ispreferably 2 vol % or more and 8 vol % or less, more preferably, 4 vol %or more and 8 vol % or less. If an addition amount of MgO increases,STOL characteristics tend to deteriorate.

Further, TCR adjustment additives other than mentioned above are, MnO₂,V₂O₅, TiO₂, Y₂O₃, Nb₂O₅, Cr₂O₃, Fe₂O₃, CoO, Al₂O₃, ZrO₂, SnO₂, HfO₂,WO₃, Bi₂O₃, etc.

Resistor paste according to the present embodiment is prepared in thesame way as the first embodiment of the present invention. The obtainedresistor comprises glass material substantially free of lead, conductivematerial substantially free of lead, and perovskite type crystalstructured oxide other than CaTiO₃. Thickness of the resistor film maybe thin but normally 1 μm or more, preferably around 10 to 15 μm or so.

The resistor according to the present embodiment can be applied to anelectrode part of a capacitor or an inductor other than a single layeror multiple layer circuit board.

Other compositions, manufacturing methods, and effects of thisembodiment of the invention are the same with those of the firstembodiment of the invention.

EXAMPLE 1

Below, the present invention is described in detail with referred toconcrete examples of the above-mentioned present embodiments. However,the present invention is not limited to the examples.

Preparation of Resistor Paste

Conductive materials were prepared as below. CaCO₃ or Ca(OH)₂ powder andRuO₂ powder were weighed to give formulation CaRuO₃, which was thenmixed by a ball mill and dried. Obtained powder was heated to 1400° C.at a rate of 5° C./min, maintained its temperature for 5 hours, andcooled to a room temperature at a rate of 5° C./min. Obtained CaRuO₃compound was grinded by a ball mill to CaRuO₃ powder. Using XRD, theobtained powder was confirmed to be CaRuO₃.

Glass materials were prepared as below. CaCO₃, B₂O₃, SiO₂, ZrO₂, andvarious oxides were weighed to give the final formulations (9 kinds) asshown in Table 1 of the invention, those were then mixed by a ball milland dried. Obtained powder was heated to 1300° C. at a rate of 5°C./min, maintained its temperature for 1 hour, and was dropped in waterto rapidly cool and vitrify. Obtained vitrified material was grinded bya ball mill to obtain glass powder. Using XRD, the obtained powder wasconfirmed to be amorphous. TABLE 1 Glass Material NumbersCompositions(mol %) {circle around (1)} CaO:B₂O₃:SiO₂:ZrO₂= 34:36:25:5{circle around (2)} CaO:B₂O₃:SiO₂ = 35:39:26 {circle around (3)}CaO:B₂O₃:SiO₂:ZrO₂= 35:33:22:10 {circle around (4)} CaO:B₂O₃:SiO₂:ZrO₂=40:33:22:5 {circle around (5)} CaO:B₂O₃:SiO₂:ZrO₂= 35:24:36:5 {circlearound (6)} CaO:B₂O₃:SiO₂:ZrO₂= 20:45:30:5 {circle around (7)}CaO:B₂O₃:SiO₂:Al₂O₃ = 34:36:25:5 {circle around (8)}CaO:B₂O₃:SiO₂:ZrO₂:ZnO = 34:32:24:5:5 {circle around (9)}CaO:B₂O₃:SiO₂:ZrO₂:MnO = 34:32:24:5:5

Organic vehicle was prepared as below. Terpineol as a solvent was heatedand stirred and by solving ethyl cellulose as a resin, organic vehiclewas prepared.

Additives were selected as shown in table 2. Prepared conductivematerial powder, glass powder, and selected additive were weighed togive each formulation as shown in Table 2, and organic vehicle wasadded, then, mixed by a three roll mill to obtain a resistor paste. Theratio of the total weight of the conductive powder, glass powder, andadditive, and the weight of the organic vehicle was adjusted to a weightratio of a range of 1:0.25 to 1:4 to prepare each resistor paste so thatthe obtained resistor paste had a viscosity suitable for screenprinting.

Preparation of Thick-Film Resistor

A 96% purity alumina substrate was screen printed with an Ag—Ptconductor paste to a predetermined shape and then dried. Ag in the Ag—Ptconductor paste was 95 wt %, and Pt was 5 wt %. This alumina substratewas placed in a belt furnace and fired by a one-hour pattern fromcarrying to carrying out. The firing temperature at this time was 850°C., and the holding time at this temperature was 10 minutes. The aluminasubstrate formed with the conductor in this way was coated with thepreviously prepared resistor paste by screen printing to a predeterminedshape (1 mm×1 mm) of a pattern. After this, the resistor paste was firedunder the same conditions as the firing of the conductor to obtain theresistor. The thickness of the resistor film was 12 μm.

Evaluation of Thick-Film Resistor Characteristics (TCR and STOL)

TCR and STOL characteristics of the obtained thick-film resistor wereevaluated. TCR was evaluated by confirming the ratio of change inresistance value when changing the temperature from room temperature of25° C. to −55° C. (the low temperature) and 125° C. (the hightemperature). Concretely, if designating the resistance values at 25°C., −55° C., and 125° C. as R25, R-55, and R125 (Ω/□), the hightemperature TCR (HTCR) and the low temperature TCR (CTCR) wererespectively found by HTCR=(R25−R125)/R25/100×1000000 (ppm/° C.),CTCR=(R25−(R-55))/R25/80×1000000 (ppm/° C.). Results are shown in Table2. Note the larger of the two values is made the TCR value of table 2.Normally, TCR<±100 ppm/° C. is a bases of its characteristic.

STOL characteristics was evaluated by confirming the ratio of change inresistance value before and after applying test voltage to thick-filmresistor for 5 seconds and leaving for 30 minutes. The test voltage was2.5×rated voltage, and the rated voltage was √{square root over ()}(R/8), where R is the resistance value (Ω/□). For resistors withresistance values with calculated test voltages over 200V, the testvoltage was made 200V. The results are shown in Table 2. Normally,STOL<±5% is a bases of its characteristic. TABLE 2 conductive glassSample material material additives sheet resistance value TCR Numberkind vol % kind vol % kind vol % Ω/□ ppm/° C. STOL % *1 CaRuO₃ 15{circle around (1)} 85 — — 177600 ±1200 −0.8 *2 CaRuO₃ 12 {circle around(1)} 87 CuO 1 132100 ±95 −13.7 3 CaRuO₃ 28 {circle around (1)} 60 NiO 12110100 ±90 −0.8 4 CaRuO₃ 26 {circle around (1)} 70 NiO 4 146700 ±100−1.5 5 CaRuO₃ 28 {circle around (2)} 68 NiO 4 109600 ±95 −5.4 6 CaRuO₃27 {circle around (3)} 69 NiO 4 115500 ±80 −6.0 7 CaRuO₃ 26 {circlearound (4)} 70 NiO 4 103300 ±100 −1.8 8 CaRuO₃ 24 {circle around (5)} 72NiO 4 150400 ±95 −2.1 9 CaRuO₃ 26 {circle around (6)} 70 NiO 4 146200±100 −2.3 10 CaRuO₃ 20 {circle around (7)} 74 NiO 6 153100 ±85 −1.9 11CaRuO₃ 22 {circle around (8)} 72 NiO 6 128800 ±75 −1.6 12 CaRuO₃ 20{circle around (9)} 77 NiO 3 134100 ±90 −3.3 13 CaRuO₃ 14 {circle around(1)} 79 NiO 6 123100 ±80 −1.2 CuO 1 14 CaRuO₃ 8 {circle around (1)} 89NiO 2 130100 ±50 −1.5 CuO 2 15 CaRuO₃ 14 {circle around (1)} 75 NiO 6114000 ±70 −0.9 CuO 1 MgO 4 *16 CaRuO₃ 12 {circle around (1)} 88 — —1067000 ±1200 −0.9 *17 CaRuO₃ 8 {circle around (1)} 91 CuO 1 1537000±160 −27.7 18 CaRuO₃ 14 {circle around (1)} 69 NiO 12 1072000 ±100 −2.5CuO 1 MgO 4 19 CaRuO₃ 12 {circle around (1)} 70 NiO 8 1481000 ±100 −4.3CuO 2 MgO 8 20 CaRuO₃ 15 {circle around (1)} 72 NiO 13 1672000 ±160 −5.5CuO 1 MgO 4 21 CaRuO₃ 22 {circle around (1)} 70 NiO 3 10060 ±80 0.0 CuO1 MgO 2 22 CaRuO₃ 15 {circle around (1)} 81 CaTiO₃ 4 356800 ±100 0.0 23CaRuO₃ 12 {circle around (1)} 78 CaTiO₃ 6 965300 ±100 −1.2 CuO 4 24CaRuO₃ 15 {circle around (1)} 65 CaTiO₃ 12 1207000 ±100 −4.8 CuO 8 25CaRuO₃ 8 {circle around (1)} 84 CaTiO₃ 4 1108000 ±95 −2.5 CuO 3 ZnO 1 26CaRuO₃ 12 {circle around (1)} 82 CaTiO₃ 2 171600 ±75 −0.5 CuO 2 ZnO 2 27CaRuO₃ 14 {circle around (1)} 74 CaTiO₃ 4 16020 ±75 0.0 CuO 4 ZnO 4 28CaRuO₃ 30 {circle around (1)} 63 CaTiO₃ 4 10060 ±60 0.0 CuO 3*are comparative examples of the invention

As shown in Table 2, the followings were found by samples 1 to 3 thosehaving or not having the additives. Sample 1 without any additive, couldsuppress STOL characteristics as low as −0.8%, however, showeddeterioration in TCR. Sample 2 comprising CuO as an additive, comparedto sample 1, could suppress TCR as low as ±95%, however, showeddeterioration in STOL characteristics as −13.7%. To the contrary, sample3 comprising NiO as an additive, could adjust TCR within ±100%, andsuppress STOL character ristics to −0.8%. Note that samples 1 and 2 arecomparative examples and sample 3 is an example of the invention.

The followings could be found by samples 4 to 12 wherein glasscompositions were varied. Sample 6 comprising glass including 10 mol %of ZrO₂ (C group), compared to sample 5 comprising glass not includingZrO₂, tends to deteriorate in STOL characteristics, however, it waswithin the tolerance level. The same tendency was found when ZrO₂ waschanged to Al₂O₃ (C group) as in sample 10. As in samples 4 and 7 to 9,their characteristics were maintained within a range of glasscompositions. An adjustment of glass compositions aim to adjust glasscharacteristics such as softening point did not effect TCR nor STOLcharacteristics. Note that when the same experiments were done exceptCaO (A group) was substituted with the same II group, i.e. MgO, SrO orBaO, the same tendencies were found. It was confirmed that when ZnO orMnO (both in D group) was further added as in sample 11 or 12, there wasno effect on TCR or STOL characteristics. Samples 4 to 12 respectivelyshow examples of the invention.

It was effective for an adjustment of TCR and STOL characteristics whenthe other additives were included in addition to NiO as in samples 13 to15 and 18 to 21. Particularly, a combination of NiO and CuO waseffective, and by further adding MgO, STOL characteristics can besuppressed low (Samples 15 and 18 to 21). However, sample 20 showeddeterioration in TCR. It may be due to a large amount of NiO included.Resistance values of 1MΩ as in samples 16 and 17 were one digit higherthan those of 100 KΩ as in samples 1 and 2. Said sample 16 not includingadditives showed the same tendency as in sample 1. And said sample 17including CuO as an additive showed the same tendency as in sample 2.Note, samples 13 to 15 and 18 to 21 are examples of the invention andsamples 16 and 17 are comparative examples of the same.

The followings may be obtained when an additive was changed from NiO toCaTiO₃ as in samples 22 to 28. When CaTiO₃ was added independently as insample 22, not much effect was shown in TCR adjustment, however,remarkable effect was shown to decrease STOL characteristics. The sameremarkable decrease in STOL characteristics was shown when the otheradditives were added in addition to CaTiO₃ as in samples 23 to 28.Particularly, a combination of CaTiO₃ and CuO was effective and when ZnOwas further added as in samples 25 to 27, STOL characteristics canfurther be decreased. Note that each of samples 22 to 28 is an exampleof the invention.

With reference to samples 21, 27 and 28, by comprising NiO or CaTiO₃ asan additive, even with a resistor having a low resistor value of 10 KΩor less, superior TCR and STOL characteristics can be obtained.

EXAMPLE 2

A resistor paste was prepared in the same way as example 1 exceptconductive material powder, glass powder, and additives were weighed togive the formulations as shown below in Table 3. Further, thick-filmresistors were prepared in the same way as example 1 of the invention,and the same measurements were done to said resistors. The results areshown in Table 3 of the invention. TABLE 3 conductive glass Samplematerial material additives sheet resistance value TCR Number kind vol %kind vol % kind vol % Ω/□ ppm/° C. STOL % *1 CaRuO₃ 15 {circle around(1)} 85 — — 177600 ±1200 −0.8 *2 CaRuO₃ 12 {circle around (1)} 87 CuO 1132100 ±95 −13.7 29 CaRuO₃ 18 {circle around (1)} 78 SrTiO₃ 4 149900 ±90−1.1 30 CaRuO₃ 18 {circle around (1)} 78 BaTiO₃ 4 268000 ±100 −2.1 31CaRuO₃ 18 {circle around (1)} 78 SrTiO₃ 2 209000 ±95 −1.5 BaTiO₃ 2 32CaRuO₃ 18 {circle around (1)} 80 CaZrO₃ 2 171500 ±95 −4.2 33 CaRuO₃ 18{circle around (1)} 80 SrZrO₃ 2 135500 ±100 −4.5 34 CaRuO₃ 28 {circlearound (2)} 68 SrTiO₃ 4 105000 ±100 −1.6 35 CaRuO₃ 27 {circle around(3)} 69 SrTiO₃ 4 130300 ±100 −4.0 36 CaRuO₃ 26 {circle around (4)} 70SrTiO₃ 4 145000 ±100 −2.8 37 CaRuO₃ 24 {circle around (5)} 72 SrTiO₃ 4162400 ±100 −3.1 38 CaRuO₃ 26 {circle around (6)} 70 SrTiO₃ 4 113500±100 −3.3 39 CaRuO₃ 20 {circle around (7)} 74 SrTiO₃ 6 180200 ±85 −2.940 CaRuO₃ 22 {circle around (8)} 72 SrTiO₃ 6 103400 ±80 −2.3 41 CaRuO₃20 {circle around (9)} 77 SrTiO₃ 3 120800 ±85 −4.0 42 CaRuO₃ 28 {circlearound (2)} 68 BaTiO₃ 4 223000 ±100 −1.9 43 CaRuO₃ 27 {circle around(3)} 69 BaTiO₃ 4 203000 ±100 −4.2 44 CaRuO₃ 26 {circle around (4)} 70BaTiO₃ 4 254400 ±100 −3.0 45 CaRuO₃ 24 {circle around (5)} 72 BaTiO₃ 4261600 ±100 −3.5 46 CaRuO₃ 26 {circle around (6)} 70 BaTiO₃ 4 210500±100 −3.6 47 CaRuO₃ 20 {circle around (7)} 74 BaTiO₃ 6 280000 ±95 −3.248 CaRuO₃ 22 {circle around (8)} 72 BaTiO₃ 6 234100 ±85 −4.4 49 CaRuO₃20 {circle around (9)} 77 BaTiO₃ 3 287500 ±90 −4.9 50 CaRuO₃ 8 {circlearound (1)} 88 SrTiO₃ 3 1317000 ±100 −2.2 CuO 1 51 CaRuO₃ 8 {circlearound (1)} 71 BaTiO₃ 13 1022000 ±95 −2.8 CuO 8 52 CaRuO₃ 18 {circlearound (1)} 63 SrTiO₃ 13 1370000 ±100 −1.3 CuO 2 ZnO 4 53 CaRuO₃ 30{circle around (1)} 66 BaTiO₃ 1 15230 ±75 −0.7 CuO 2 ZnO 1 54 CaRuO₃ 16{circle around (1)} 76 SrTiO₃ 4 121900 ±80 −2.6 CuO 2 MgO 2 55 CaRuO₃ 15{circle around (1)} 71 BaTiO₃ 4 253700 ±100 −4.1 CuO 2 MgO 8 56 CaRuO₃10 {circle around (1)} 69 SrTiO₃ 1 120300 ±80 −3.3 CuO 8 NiO 12 57CaRuO₃ 12 {circle around (1)} 80 BaTiO₃ 4 237200 ±100 −3.3 CuO 3 NiO 158 CaRuO₃ 15 {circle around (1)} 81 NiTiO₃ 4 563400 ±95 −2.1 59 CaRuO₃15 {circle around (1)} 81 MnTiO₃ 4 231100 ±90 −4.0 60 CaRuO₃ 15 {circlearound (1)} 81 CoTiO₃ 4 197800 ±100 −4.1 61 CaRuO₃ 15 {circle around(1)} 81 FeTiO₃ 4 277300 ±100 −4.4 62 CaRuO₃ 15 {circle around (1)} 81CuTiO₃ 4 152100 ±85 −3.7 63 CaRuO₃ 15 {circle around (1)} 81 MgTiO₃ 4303000 ±80 −0.5*are comparative examples of the invention

As shown in Table 3, the followings were found by samples 1, 2 and 29 to33, those depending on the additives. Sample 1 without any additive,could suppress STOL characteristics as low as −0.8%, however, showeddeterioration in TCR. Sample 2 comprising CuO as an additive, comparedto sample 1, could suppress TCR as low as ±95%, however, showeddeterioration in STOL characteristics as −13.7%. To the contrary,samples 29 to 33, comprising at least SrTiO₃ or BaTiO₃ as an additive,could adjust TCR within ±100%, and suppress STOL characteristics to−0.8%. Note samples 1 and 2 are comparative examples and samples 29 to33 are examples of the invention.

The followings could be found by samples 34 to 49 wherein glasscompositions were varied. Samples 35 and 43 comprising glass including10 mol % of ZrO₂ (C group), compared to samples 34 and 42 comprisingglass not including ZrO₂, tends to deteriorate in STOL characteristics,however, it was within the tolerance level. The same tendency was foundwhen ZrO₂ was changed to Al₂O₃ (C group) as in samples 39 and 47. As insamples 39 to 41 and 47 to 49, their characteristics were maintainedwithin a range of glass compositions. An adjustment of glasscompositions aim to adjust glass characteristics such as softening pointdid not effect TCR nor STOL characteristics. Note that when the sameexperiments were done except CaO (A group) was substituted with the sameII group, i.e. MgO, SrO or BaO, the same tendencies were found. It wasconfirmed that when ZnO or MnO (both in D group) was further added as insamples 40, 41, 48 and 49, there was no effect on TCR or STOLcharacteristics. Note samples 34 to 49 respectively show examples of theinvention.

It was effective for an adjustment of TCR and STOL characteristics whenthe other additives were included in addition to SrTiO₃ and BaTiO₃ as insamples 50 to 57. Particularly, a combination of SrTiO₃ or BaTiO₃ andCuO was effective, and by further adding MgO and/or NiO, STOLcharacteristics can be suppressed low.

Further, when glass material of {circle around (1)} as in Table 1 andadditives of NiTiO₃, MnTiO₃, CoTiO₃, FeTiO₃, CuTiO₃, MgTiO₃ instead ofSrTiO₃ or BaTiO₃ as in samples 58 to 63 were used, the same effects wereobtained when SrTiO₃ or BaTiO₃ were added. Note that samples 50 to 63are examples of the invention.

While the invention has been described with reference to specificembodiments chosen for purpose of illustration, it should be apparentthat numerous modifications could be made thereto by those skilled inthe art without departing from the basic concept and scope of theinvention.

1. A resistor paste comprising glass material substantially free oflead, conductive material substantially free of lead, organic vehicle,and NiO as an additive.
 2. The resistor paste as set forth in said claim1, comprising: 60 vol % or more and less than 91 vol % of glass materialand 8 vol % or more and 32 vol % or less of conductive material.
 3. Theresistor paste as set forth in claim 1 or 2, comprising more than 0 vol% and 12 vol % or less of NiO.
 4. The resistor paste as set forth inclaim 3, comprising 2 vol % or more and 12 vol % or less of NiO.
 5. Theresistor paste as set forth in any one of the claims 1 to 4, furthercomprising CuO as an additive and a content of said CuO is more than 0vol % and 8 vol % or less.
 6. The resistor paste as set forth in claim5, comprising: 2 vol % or more and 12 vol % or less of NiO and more than1 vol % and 2 vol % or less of CuO.
 7. A resistor paste comprising:glass material substantially free of lead, conductive materialsubstantially free of lead, organic vehicle and CaTiO3 as an additive.8. The resistor paste as set forth in claim 7, comprising: 63 vol % ormore and 84 vol % or less of the glass material and 8 vol % or more and30 vol % or less of the conductive material.
 9. The resistor paste asset forth in claim 7 or 8, further comprising CuO as an additive and acontent of said CuO is more than 0 vol % and 8 vol % or less.
 10. Theresistor paste as set forth in claim 9, comprising 1 vol % or more and 2vol % or less of CuO.
 11. The resistor paste as set forth in any one ofthe claims 7 to 10, comprising more than 0 vol % and 13 vol % or less ofCaTiO3.
 12. The resistor paste as set forth in claim 9, comprising 2 vol% or more and less than 12 vol % of CaTiO3 and 2 vol % or more and lessthan 8 vol % of CuO.
 13. The resistor paste as set forth in any one ofthe claims 7 to 12, further comprising NiO as an additive and a contentof Ni is more than 0 vol % and 12 vol % or less.
 14. The resistor pasteas set forth in claim 13 comprising 2 vol % or more and 12 vol % or lessof NiO.
 15. A resistor paste comprising glass material substantiallyfree of lead, conductive material substantially free of lead, organicvehicle, and perovskite type crystal structured oxide as an additive.16. The resistor paste as set forth in claim 15 wherein said perovskitetype crystal structured oxide is at least one kind from CaTiO3, SrTiO3,BaTiO3, NiTiO3, MnTiO3, CoTiO3, FeTiO3, CuTiO3, MgTiO3.
 17. The resistorpaste as set forth in claim 15 or 16 comprising: 63 vol % or more and 88vol % or less of glass material and 8 vol % or more and 30 vol % or lessof conductive material.
 18. The resistor paste as set forth in any oneof the claims 15 to 17 wherein a content of said perovskite type crystalstructured oxide is more than 0 vol % and 13 vol % or less.
 19. Theresistor paste as set forth in any one of the claims 15 to 18 furthercomprising CuO as an additive and a content of said CuO is more than 0vol % and 8 vol % or less.
 20. The resistor paste as set forth in anyone of the claims 15 to 19 further comprising NiO as an additive and acontent of said NiO is more than 0 vol % and 12 vol % or less.
 21. Theresistor paste as set forth in any one of the claims 1 to 20, furthercomprising MgO as an additive and a content of said MgO is 2 vol % ormore and 8 vol % or less.
 22. The resistor paste as set forth in any oneof the claims 1 to 21, further comprising ZnO as an additive and acontent of said ZnO is 1 vol % or more and 4 vol % or less.
 23. Theresistor paste as set forth in claim 19, comprising: 1 vol % or more andless than 12 vol % of perovskite type crystal structured oxide, and 1vol % or more and less than 8 vol % of CuO.
 24. The resistor paste asset forth in any one of claims 1 to 23, comprising: A group comprisingat least one kind from CaO, SrO, BaO, and MgO, B group comprising B2O3and/or SiO2, and C group comprising ZrO2 and/or Al₂O₃.
 25. The resistorpaste as set forth in claim 24, wherein said glass material furthercomprises D group selected at least one kind from ZnO, MnO, CuO, CoO,Li2O, Na2O, K2O, P2O5, TiO2, Bi2O3, V2O5 and Fe2O3.
 26. The resistorpaste as set forth in claim 24, wherein contents of said groups are: Agroup of 20 mol % or more and 40 mol % or less, B group of 55 mol % ormore and 75 mol % or less and C group of more than 0 mol % and less than10 mol %.
 27. The resistor paste as set forth in claim 25, comprising Dgroup of 0 mol % or more and 5 mol % or less.
 28. The resistor paste asset forth in any one of the claims 1 to 27, comprising the conductivematerial including RuO2 or complex oxides of Ru.
 29. The resistor pasteas set forth in any one of the claims 1 to 28, wherein the ratio (W2/W1)between the weight (W1) of all powders of glass material, conductivematerial, and additive and the weight (W2) of organic vehicle is 0.25 to4.
 30. A resistor comprising glass material substantially free of lead,conductive material substantially free of lead, and NiO as an additive.31. A resistor comprising glass material substantially free of lead,conductive material substantially free of lead, and CaTiO3 as anadditive.
 32. A resistor comprising glass material substantially free oflead, conductive material substantially free of lead, perovskite typecrystal structure oxide as an additive.
 33. An electric device having aresistor paste, wherein said resistor paste comprising: glass materialsubstantially free of lead, conductive material substantially free oflead, and NiO as an additive.
 34. An electric device having a resistorpaste, wherein said resistor paste comprising: glass materialsubstantially free of lead, conductive material substantially free oflead, and CaTiO3 as an additive.
 35. An electric device having aresistor paste, wherein said resistor paste comprising: glass materialsubstantially free of lead, conductive material substantially free oflead, and perovskite type crystal structured oxide as an additive.